Little is known regarding the effects of damage to specific regions of the human brain when this damage occurs early in life, although there is reason to believe that certain impairments of cognition and behavior are a consequence of early-onset brain damage. The NINDS has identified as high research priorities the gathering of more precise descriptions of behavior patterns and developmental disorders, and the achievement of greater understanding of the neural basis of cognition, emotion, and their interaction. Lesion method studies of individuals who have sustained early-onset focal brain damage are an important means to fulfill such priorities, and during the current funding period we have conducted pilot studies of adults with early-onset focal brain damage and marked cognitive and behavioral impairments. Conditions causing focal brain damage in childhood are not common, but a sufficient number of patients is now available for systematic studies. Here we propose to establish a registry of patients with damage to circumscribed brain regions acquired during development, namely during the perinatal period, infancy, childhood, or adolescence, and to perform hypothesis-driven studies of these individuals using: (1) precise description of brain lesions using MRI with 3-D reconstruction, (2) comprehensive characterization of cognition and behavior with standardized, age-appropriate neuropsychological measures, (3) standardized indices of functional outcome (academic achievement, employment, quality of life, and family burden), and (4) experimental measures of cognition and behavior, with a focus on emotion, moral reasoning and social competence Delineation of relationships between damage to specific neural systems early in life and the short- and long-term consequences for cognition and behavior should provide fundamental information which will be relevant to the understanding of human development, and permit better evaluation and treatment of treatment of neurobehavioral disorders with onset in childhood.